Condensed Consolidating Financial Statements (Cash Flows) (Details) - USD ($) $ in Thousands	9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Apr. 30, 2016	Apr. 30, 2015
Condensed Financial Statements, Captions [Line Items]
Net cash used in operating activities:	$ (1,375,917)	$ (1,426,949)
Sales, maturities of and payments received on AFS securities	144	436,380
Principal payments and sales of mortgage loans and real estate owned, net	207,174	28,004
Capital expenditures	(73,924)	(66,418)
Payments made for business acquisitions, net of cash acquired	(52,825)	(85,329)
Loans made to franchisees	(31,788)	(21,377)
Repayments from franchisees	20,816	22,234
Other, net	(4,855)	547
Net cash provided by (used in) investing activities	64,742	314,041
Repayments of Long-term Lines of Credit	(445,000)	(225,000)
Proceeds from Long-term Lines of Credit	1,545,000	1,350,000
Proceeds from Issuance of Long-term Debt	0	996,831
Customer banking deposits, net	0	(326,705)
Transfer of bank deposits	0	(419,028)
Dividends paid	(141,537)	(157,530)
Repurchase of common stock, including shares surrendered	(322,782)	(1,888,595)
Proceeds from exercise of stock options	2,403	25,803
Other, net	373	(43,972)
Net cash used in financing activities	638,457	(688,196)
Effects of exchange rates on cash	(2,911)	(16,575)
Net decrease in cash and cash equivalents	(675,629)	(1,817,679)
Cash & cash equivalents	221,172	189,511	$ 896,801	$ 2,007,190
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends paid	(141,537)	(157,530)
Repurchase of common stock, including shares surrendered	(322,782)	(1,888,595)
Proceeds from exercise of stock options	2,403	25,803
Intercompany borrowings (payments)	461,916	2,024,025
Other, net		(3,703)
Block Financial Issuer [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash used in operating activities:	(399,367)	(403,132)
Sales, maturities of and payments received on AFS securities	144	430,460
Principal payments and sales of mortgage loans and real estate owned, net	207,174	28,004
Capital expenditures	(14)	(24)
Loans made to franchisees	(31,568)	(20,940)
Repayments from franchisees	20,605	22,006
Intercompany borrowings (payments)	(891,350)	(1,871,617)
Other, net	(10,377)	(8,795)
Net cash provided by (used in) investing activities	(705,386)	(1,420,906)
Repayments of Long-term Lines of Credit	(445,000)	(225,000)
Proceeds from Long-term Lines of Credit	1,545,000	1,350,000
Proceeds from Issuance of Long-term Debt		996,831
Customer banking deposits, net		(327,145)
Transfer of bank deposits		(419,028)
Other, net		(19,282)
Net cash used in financing activities	1,100,000	1,356,376
Net decrease in cash and cash equivalents	(4,753)	(467,662)
Cash & cash equivalents	4,272	10,415	9,025	478,077
Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash used in operating activities:	(976,550)	(1,023,817)
Sales, maturities of and payments received on AFS securities		5,920
Capital expenditures	(73,910)	(66,394)
Payments made for business acquisitions, net of cash acquired	(52,825)	(85,329)
Loans made to franchisees	(220)	(437)
Repayments from franchisees	211	228
Intercompany borrowings (payments)	(461,916)	(2,024,025)
Other, net	5,522	9,342
Net cash provided by (used in) investing activities	(583,138)	(2,160,695)
Intercompany borrowings (payments)	891,350	1,871,617
Other, net	373	(20,987)
Net cash used in financing activities	891,723	1,850,630
Effects of exchange rates on cash	(2,911)	(16,575)
Net decrease in cash and cash equivalents	(670,876)	(1,350,457)
Cash & cash equivalents	216,900	179,096	$ 887,776	1,529,553
Intersegment Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Intercompany borrowings (payments)	1,353,266	3,895,642
Net cash provided by (used in) investing activities	1,353,266	3,895,642
Customer banking deposits, net		440
Intercompany borrowings (payments)	(1,353,266)	(3,895,642)
Net cash used in financing activities	$ (1,353,266)	(3,895,202)
Net decrease in cash and cash equivalents		$ 440
Cash & cash equivalents				$ (440)